Circuitry to control a switching regulator

ABSTRACT

In one aspect, a circuit includes a switching regulator configured to provide power to a load, a current regulator circuit coupled to the load and a response circuit configured to provide a control signal to the switching regulator in response to electrical changes of the current regulator circuit. The control signal changes non-linearly with respect to the electrical changes at the current regulator circuit. In another aspect, a circuit includes an adaptive regulation voltage circuit configured to provide a regulation voltage to a first input of an amplifier to maintain operability of a current regulator circuit. The adaptive regulation voltage circuit replicates electrical characteristics of the current regulator circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 12/966,139 filed on Dec. 13, 2010, which isincorporated herein by reference in its entirety.

BACKGROUND

A variety of electronic circuits are used to drive diode loads and, moreparticularly, to control electrical current through strings ofseries-connected light-emitting diodes (LEDs), which, in some examples,form an LED display, or, more particularly, a backlight for a display,for example, a liquid crystal display (LCD). It is known that individualLEDs have a variation in forward voltage drop from unit to unit.Therefore, the strings of series-connected LEDs can have a variation inforward voltage drop.

Strings of series-connected LEDs can be coupled to a common switchingregulator, e.g., a boost switching regulator, at one end of the LEDstrings, the switching regulator configured to provide a high enoughvoltage to supply each of the strings of LEDs. The other end of each ofthe strings of series-connected LEDs can be coupled to a respectivecurrent sink, configured to sink a relatively constant current througheach of the strings of series-connected LEDs.

It will be appreciated that the voltage generated by the commonswitching regulator must be a high enough voltage to supply the oneseries-connected string of LEDs having the greatest total voltage drop,plus an overhead voltage needed for proper operation of the respectivecurrent sink. In other words, if four series-connected strings of LEDshave voltage drops of 30 Volts, 30 Volts, 30 Volts, and 31 Volts, andeach respective current sink requires at least one volt in order tooperate, then the common boost switching regulator must supply at least32 Volts.

SUMMARY

In one aspect, a circuit includes a switching regulator configured toprovide power to a load, a current regulator circuit coupled to the loadand a response circuit configured to provide a control signal to theswitching regulator in response to electrical changes of the currentregulator circuit. The control signal changes non-linearly with respectto the electrical changes at the current regulator circuit.

In another aspect, a circuit includes a switching regulator configuredto provide power to a load, a current regulator circuit coupled to theload and an adaptive response circuit. The adaptive response circuitincludes an amplifier configured to provide a control signal to theswitching regulator in response to electrical changes at the currentregulator. The adaptive response circuit includes a first input and asecond input coupled to the current regulator circuit and an adaptiveregulation voltage circuit configured to provide a regulation voltage tothe first input of the amplifier to maintain operability of the currentregulator circuit. The adaptive regulation voltage circuit replicateselectrical characteristics of the current regulator circuit.

DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention, as well as the invention itselfmay be more fully understood from the following detailed description ofthe drawings, in which:

FIG. 1A is block diagram of a circuit to drive a load;

FIG. 1B is a block diagram of an example of the circuit in FIG. 1A thatincludes a string of light emitting diodes (LEDs) as the load;

FIG. 1C is a block diagram of another example of the circuit of FIG. 1Athat includes multiple strings of LEDs as the load;

FIG. 2A is a block diagram of an example of a non-linear responsecircuit and an example of a current regulator circuit;

FIG. 2B is a graph of current versus change of current for anexponential inverting transconductance amplifier;

FIG. 2C is a circuit diagram of an example of a DC-DC converter;

FIG. 3A is a block diagram of other examples of the non-linear responseand the current regulator circuits;

FIG. 3B is a block diagram of a further example of the non-linearresponse circuit;

FIG. 4 is a circuit diagram of a current sink circuit;

FIG. 5 is a circuit diagram of a current detection circuit;

FIG. 6A is block diagram of another circuit to drive the load;

FIG. 6B is a block diagram of an adaptive response circuit; and

FIGS. 7A and 7B are circuit diagrams of examples of adaptive regulationvoltage circuits.

DETAILED DESCRIPTION

Before describing the present invention, some introductory concepts andterminology are explained. The term “boost switching regulator” is usedto describe a known type of switching regulator that provides an outputvoltage higher than an input voltage to the boost switching regulator.While a certain particular circuit topology of boost switching regulatoris shown herein, it should be understood that boost switching regulatorshave a variety of circuit configurations. As used herein, the term “buckswitching regulator” is used to describe a known type of switchingregulator that provides an output voltage lower than an input voltage tothe buck switching regulator. It should be understood that there arestill other forms of switching regulators other than a boost switchingregulator and other than a buck switching regulator, and this inventionis not limited to any one type.

DC-DC converters are described herein and the described DC-DC converterscan be any form of switching regulator, including, but not limited to,the above-described boost and buck switching regulators.

As used herein, the term “current regulator” is used to describe acircuit or a circuit component that can regulate a current passingthrough the circuit or circuit component to a predetermined, i.e.,regulated, current. A current regulator can be a “current sink,” whichcan input a regulated current, or a “current source,” which can output aregulated current. A current regulator has a “current node” at which acurrent is output in the case of a current source, or at which a currentis input in the case of a current sink.

Described herein are various embodiments including circuitry andtechniques to control a switching regulator that supplies a regulatedoutput voltage to a load, which load in turn is controlled by a currentregulator circuit. In one set of embodiments, the circuitry isconfigured to provide a non-linear increase in a control signal providedto the switching regulator in response to a decrease in a voltage at aload. In this way, the switching regulator can respond faster thanotherwise possible to a step response that results in a drop inregulated output voltage provided to the load. In one example, thecircuitry includes a non-linear amplifier that is configured to providea higher-than-linear increase in the control signal level in response toa decrease in the current regulator voltage.

In another embodiment, an adaptive regulation voltage circuit isconfigured to provide sufficient voltage to one or more currentregulators regardless of temperature, processing constraints and otherelectrical constraints to ensure current regulator circuits maintainoperability. Other embodiments will be apparent to one of ordinary skillin the art in view of the specification.

Referring to FIG. 1A, a circuit 10 includes an electronic circuit 20(e.g., an integrated circuit (IC)) to drive a load 40. The circuit 10also includes a capacitor 44 with one end of the capacitor coupled tothe load 40 and the other end of the capacitor coupled to ground. In oneexample, the capacitor 44 functions as a filter. The electronic circuit20 includes a DC-DC converter 32 that is configured to receive an inputvoltage, Vin, from a power source (not shown) via a connection 52 and toprovide a regulated output voltage, Vout, to the load 40 through aconnection 54 in response to a control signal 58.

The electronic circuit 20 also includes a current regulator circuit 34coupled to the load 40 by a connection 56. The electronic circuit 20also includes a non-linear response circuit 36 that is coupled to thecurrent regulator circuit 34 by a connection 55 and is coupled to theDC-DC converter 32 by a connection 58.

The various connections described herein may be referred to hereininterchangeably with the signal carried by the respective connection.For example, reference character 52 may be used interchangeably to referto the connection to the DC-DC converter 32 and to the input voltage,Vin, associated with such a connection.

In one example, the non-linear response circuit 36 provides a controlsignal 58 to the DC-DC converter 32 responsive to electrical changes atthe current regulator circuit 34. The control signal 58 controls theregulated voltage Vout provided at the output of the DC-DC converter 32.In particular, the control signal 58 changes non-linearly with respectto the electrical changes at the current regulator circuit 34. In oneparticular example, as a voltage at the current regulator circuit 34drops, the control signal 58 increases non-linearly (e.g., FIGS. 2A, 2C,2D). In one example, the non-linear increase is an exponential increase.

In some embodiments, the current regulator circuit 34, which is shown tobe coupled to the bottom of the load 40 can instead be at the top of theload. In these embodiments, a regulator input node receives theregulated voltage, Vreg, and a regulator output node is coupled to theload.

Referring to FIGS. 1B and 1C, in some examples, the load 40 may be oneor more strings of one or more series-connected light emitting diodes(LEDs). For example, in FIG. 1B, a circuit 10′ includes a string 140 ofseries-connected LEDs (e.g., an LED 40 a, an LED 40 b, . . . , an LED40N) as the load 40. In another example, in FIG. 1C, a circuit 10″includes a plurality of strings (e.g., a string 240 a, . . . , a string240N) each having a set of series-connected LEDs (e.g., the string 240 aincludes an LED 340 a, an LED 340 b, . . . , an LED 340N and the string240N includes an LED 342 a, an LED 342 b, . . . , and an LED 342N). Inone example, each of the strings 240 a-240N is coupled to a respectivecurrent regulator circuit 34 a-34N and each of the current regulatorcircuits 34 a-34N is connected to a multi-input non-linear responsecircuit 37 that includes, for example, a multi-input amplifier (notshown). An illustrative multi-input amplifier is found in U.S. PatentApplication Publication Number 2009/0128045, published May 21, 2009,entitled “ELECTRONIC CIRCUITS FOR DRIVING SERIES CONNECTED LIGHTEMITTING DIODE STRINGS,” which is incorporated herein by reference inits entirety.

In one example, one or more of the current regulators 34 a-34N may beone or more of the current regulators described herein (e.g., a currentregulator circuit 34′ (FIG. 2A) and a current regulator circuit 34″(FIG. 3A)). While FIGS. 1B and 1C include LEDs as examples of the load40, other electrical components may be used as the load 40.

Referring to FIG. 2A, in one example, the current regulator circuit 34(FIGS. 1A, 1B) may be configured as a current regulator circuit 34′ andthe non-linear response circuit 36 (FIGS. 1A, 1B) may be configured as anon-linear response circuit 36′. The current regulator circuit 34′, herein the form of a current sink, includes a current sink 108 having oneend 108 b coupled to ground and the other end 108 a coupled to the load40 (FIG. 1) by the connection 56 and to the non-linear response circuit36 by the connection 55. The non-linear response circuit 36′ includes anon-linear amplifier 110 (e.g., a non-linear transconductance amplifier)that has one input coupled to the current regulator circuit 34′ by theconnection 55 and a second input coupled to a regulation voltage circuit112 that provides a regulation voltage, Vreg, to the amplifier 110 thatis selected to guarantee sink current operation. In one illustrativeexample, the regulation voltage, Vreg, is on the order of 650 mV.

The output of the non-linear amplifier 110 is coupled to a capacitor 124(sometimes referred to as a compensation capacitor). The capacitor 124can be comprised of an output capacitance of the amplifier 110 inparallel with an input capacitance of a node 32 b (see FIG. 2A) of theDC-DC converter 32. However, in other arrangements, the capacitor 124can include other capacitors as well. The capacitor 124 can have a valueselected to stabilize a feedback control loop. In one example, thecapacitor 124 has capacitance on the order of 10 nanofarads (nF). Inother examples, a resistor (not shown) may be added in series with thecapacitor 124 to enable a faster feedback response.

The non-linear amplifier 110 has a variable non-linear gain such thatits output current varies in a non-linear fashion in response to adifference, or error voltage, between its inputs. In some arrangements,the amplifier 110 is a transconductance amplifier that provides avoltage current output. In these arrangements, the output stage of theamplifier charges or discharges the capacitor 124 according to the inputsignal levels and the transfer function of the amplifier 110 in order tothereby adjust the control signal 58 accordingly.

In one example, the non-linear amplifier 110 implements an exponentialfunction, such that an output current of the amplifier increases anddecreases exponentially with decreases and increases in the differencevoltage between its inputs, respectively. An illustrative example of anon-linear transfer function is shown in FIG. 2B.

In operation, as the voltage at the current regulator node 108 adecreases below the regulation voltage Vreg, the amplifier outputincreases in greater than a linear fashion so as to essentially “overamplify” such input voltage differences and cause the DC-DC converter torespond faster than otherwise possible. In this way, the non-lineartransfer function of the amplifier 110 provides a quicker response tolarge step responses (e.g., an increase in the supply voltage, Vin,provided to the DC-DC converter 32 or a significant load increase) thana linear amplifier. In particular, if a step-response, for example inthe form of an increased load, causes a drop in the regulated outputvoltage, Vout, then the voltage at the connection 55 will drop.Typically, a current regulator 34 can regulate down to a voltage ofapproximately 650 mV, below which the load 40 may not be supplied withsufficient current, resulting in the LEDs dimming or turning offentirely. If the step response is so large as to cause the voltage atthe current regulator to drop below 650 mV, such as to a level ofapproximately 350 mV, the amplifier 110 would sense only 300 mV betweenits inputs, an error which would not be enough to reach the amplifieroutput current limit. By using a non-linear amplifier 110 that canquickly reach its current limit, and therefore, provides a non-linearlyvarying control signal to the DC-DC converter 32, the DC-DC convertercan provide a regulated output voltage Vout that can increase fastenough to account for sudden voltage drops.

Referring to FIG. 2C, one example of the DC-DC converter 32 (FIG. 1A) isa DC-DC converter 32′. The DC-DC converter 32′ includes a first portion114 that can be within the above-described electronic circuit 20, and asecond portion 116 that can be external to but coupled to the electriccircuit 20.

The first portion 114 includes a pulse width modulation (PWM) controller118 configured to receive the control signal 58 from the non-linearresponse circuit 36 of FIG. 1A. The PWM controller 118 is configured togenerate a PWM signal 120. A control current passing element, forexample, a field-effect transistor (FET) 122, is coupled to receive thePWM signal 120 at a gate node and to receive a pulsed current signal 123at a drain node.

The second portion 116 includes an input capacitor 126 coupled betweenthe input voltage, Vin, received at the node 32 c and a ground. Aninductor 128 includes an input node 128 a also coupled to receive theinput voltage, Vin, and an output node 128 b coupled to the drain nodeof the FET 122. A diode 130 includes an anode coupled to the output node128 b of the inductor 128 and a cathode coupled to the converter outputnode 32 a, at which the regulated output voltage, Vout, is generated. Anoutput capacitor 134 is coupled between the output node 32 a and ground.The illustrated converter 32′ operates in the manner of a conventionalPWM boost switching regulator, to increase the duty cycle of the switch122 and thus the regulated output voltage, Vout, in response to anincreasing control signal 58. It will be appreciated by those ofordinary skill in the art that the PWM oscillator 118 and control signal58 may implement current or voltage node duty cycle control.

Referring to FIG. 3A, another example of the current regulator circuit34 (FIG. 1A) is a current regulator circuit 34″ and another example ofthe non-linear response circuit 36 (FIG. 1A) is a non-linear responsecircuit 36″. The current regulator circuit 34″, here again in the formof a current sink, includes a current sink 214 having one node 214 bcoupled to ground and another node 214 a coupled to the load by theconnection 56 and to the non-linear circuit 36 by the connection 55. Thenon-linear response circuit 36″ includes a linear amplifier 210(sometimes called a “boost error amplifier”) that includes one inputcoupled to the current regulator circuit 34′ by the connection 55 and asecond input coupled to a regulation voltage circuit 212 (similar toregulation voltage circuit 112 of FIG. 2A) that provides regulationvoltage, Vreg, that is selected to guarantee sink current operation. Theoutput of the non-linear amplifier 210 is coupled to the DC-DC converter32 by the connection 58 and is coupled to a capacitor 224 (similar tocapacitor 124 in FIG. 2A). The capacitor 224 can provide a loop filterand can have a value selected to stabilize a feedback control loop. Inone example, the capacitor 224 is on the order of 10 nF. In otherexamples, a resistor (not shown) may be added in series with thecapacitor 224 to enable a faster feedback response.

The non-linear response circuit 36″ also includes a current detectioncircuit 220 coupled to the capacitor 224 and to the DC-DC converter 32by the connection 58. The current detection circuit 220 is also coupleddirectly or indirectly to a node 214 c of the current sink 214 by aconnection 254. The current detection circuit 220 determines if thecurrent through the current sink 214 drops to a predetermined thresholdlevel (e.g., starts to drop).

In one particular example, the current detection circuit determines ifthe current drops by detecting if the current sink 215 is saturated. Ifthe current detection circuit 220 detects that the current drops to thepredetermined threshold level, as may be indicative of saturation of thecurrent sink or some other current level condition, the currentdetection circuit 220 will supply additional current, for example, tothe compensation capacitor 224 thereby increasing its voltage and thecontrol signal level 58 concomitantly.

Referring to FIG. 3B, another example of the non-linear response circuit36 (FIG. 1A) is the non-linear response circuit 36′″. The non-linearresponse circuit 36′″ is similar to the non-linear response circuit 36″(FIG. 3A) except a current detection circuit 220′ (similar to thecurrent detection circuit 220) is instead coupled to the linearamplifier 210 rather than being coupled to the amplifier output as isdone in the embodiment of FIG. 3A. In this configuration, if the currentdetection circuit 220′ detects that the current through the current sink214 dropped to the predetermined threshold level, such as may beindicative of saturation (or some other current level condition), thecurrent detection circuit 220′ will enable the linear amplifier 210 toprovide additional current at the amplifier output, which currentincreases the voltage on the compensation capacitor 224 and the level ofthe control signal 58 accordingly. For example, the current detectioncircuit 220′ enables an output stage of the linear amplifier 210 toinject more current at the output of the linear amplifier 210.

Referring to FIG. 4, one example of the current sink 214 (FIG. 3A) is acurrent sink 214′. The current sink 214′ includes a FET 360 having afirst terminal (e.g., a drain of the FET 360) coupled to the load 40 bythe connection 56 and to the non-linear response circuit 36″ (FIG. 3A)by the connection 55, and a second terminal (e.g., a source of the FET360) coupled to ground through a resistor 362 having a value R_(x). Thegate of the FET 260 is coupled to an output of an amplifier 364 by aconnection 382. One input of the amplifier 364 is coupled to the secondterminal (e.g., the source) of the FET 360. Another input of theamplifier 364 is coupled to a current source 392, which is coupled toground through a resistor 394. Current source 392 is coupled to a supplyvoltage, Vcc.

The current sink 214′ is designed to draw a desired current through therespective LED string in order to achieve a desired operation for theLEDs (i.e., a desired illumination). To this end, the current source 392provides a user specified current according to the specificationsparticular to the respective LED load. The amplifier 364 is arrangedsuch that the FET 360 conducts so as to draw the same current throughthe FET 360 and resistor 362 as is provided by the current source 392.In this configuration, voltage at the node 396 is the same as thevoltage at node 398; hence, current through the resistor 394 is the sameas the current through resistor 362 if both resistors are equal invalue. In other examples, the resistors may be scaled such that theoutput resistor 362 is smaller than the resistor 394 and draws morecurrent. In one particular example, a scaling factor of 1000 is usedwhere 1 uA on the reference side produces 1 mA of current through theLEDs.

In one example, the current source 392 has current equal to I_(user),which is a current set by a user. Voltage at the node 392 may besupplied to other parallel current regulators circuits (e.g., as shownin FIG. 1C), without need of a separate current regulator and resistor(392 and 394) in each current regulator circuit.

Referring to FIG. 5, in one example, the current detection circuit 220or 220′ (FIGS. 3A and 3B) may detect current saturation by measuring thevoltage at a gate of the FET 360 in the current sink 214′. Inparticular, a current detection circuit 220″ includes a comparator 282having a first input coupled to the gate of the FET 360 by theconnection 254 and a second input connected to a voltage equal to asaturation voltage, Vsat, which can be near to a saturation voltage ofthe amplifier 364 (FIG. 4).

Referring to FIGS. 6A and 6B, in which like elements have like referencecharacters, an alternative electronic circuit 22 includes an adaptiveresponse circuit 406. The adaptive response circuit 406 includes anamplifier 410 having one input coupled to the current regulator circuit34 through the connection 55 and a second input coupled to an adaptiveregulation voltage circuit 412. The adaptive regulation voltage circuit412 is configured to provide to the amplifier 410 a regulation voltage,Vreg, through a connection 420.

Typically, for example, as shown in FIG. 3A, a regulation voltage is afixed voltage chosen to guarantee that for worst-case scenarios, interms of temperature, processing constraints and other electricalconstraints, the current regulator circuit 34 (FIG. 1A) is provided withsufficient voltage for proper operation. As a result, this regulationvoltage tends to be much higher than necessary under normal operatingconditions, resulting in unnecessarily high power dissipation. Incontrast, the adaptive regulation voltage circuit 412 provides aregulation voltage 420 that is determined based on actual operatingconditions, thereby resulting in a regulation voltage, Vreg, that islower than necessary to accommodate worst case scenarios but high enoughto ensure proper operation of the current regulator 34. In particular,the adaptive regulation voltage circuit 412 includes circuitry that“mimics” or replicates the current regulator circuit 34 and isconfigured to determine a drop off voltage level of the currentregulator circuit, i.e., a voltage at which the current regulator 34ceases to operate properly. The adaptive regulation voltage circuit 412provides the regulation voltage 420 at a level above the drop offvoltage level. For example, the circuitry in the adaptive regulationvoltage circuit 412 may be a scaled down version of the currentregulator circuit 34 but with comparable physical and electricalcharacteristics. Thus, if there are conditions (e.g., temperature) thataffect the current regulator circuit 34 and in particular its drop offvoltage, the adaptive regulation circuit 412 will correspondingly adjustthe regulation voltage 420, since it will be affected in substantiallythe same manner.

Referring to FIG. 7A, one example of the adaptive regulation voltagecircuit 412 (FIG. 6B) is an adaptive regulation voltage circuit 412′.The adaptive regulation voltage circuit 412′ includes a current source424 coupled at one end to a voltage supply, Vcc, and coupled at anotherend to a resistor 426 which is further coupled to a voltage source 428.The current source 424 is a current mirror of the current source 392(FIG. 4) of the current sink circuit 214′. The resistor 426 is a scaledversion of the resistors 394 and 362 (FIG. 4). For example, theresistance is equal to N*R_(x), where N≧1. Likewise, the current source424, though being a mirror of current source 392, is scaled so that thecurrent provided is equal to (1/N)*I_(user).

The voltage source 428 represents an amount of headroom required toallow proper operation of the current sink 214′ (FIG. 4). In thisconfiguration, the regulation voltage 420 (See also FIG. 6B) is providedbetween the current source 424 and the resistor 426.

In one example, if a worse case scenario assumed a regulation voltage of650 mV, the voltage source 428 provided by the adaptive regulationvoltage circuit 412′ may be reduced to 350 mV, for example, at roomtemperature. It will be recognized that the voltage provided by thevoltage source 428 is related to a voltage headroom required by thecurrent sink 214′ (FIG. 4). As voltages within the circuit 412′ change,for example, due to temperature, the regulation voltage 428 will changein substantially the same manner. Reduced power consumption by thecircuit 412′ results.

Referring to FIG. 7B, another example of the adaptive regulation voltagecircuit 412 (FIG. 6B) is an adaptive regulation voltage circuit 412″.The adaptive regulation voltage circuit 412″ includes a current source432 coupled at one end to a voltage supply, Vcc, and the other endcoupled to a first terminal (e.g., a drain) of a FET 434. A secondterminal (e.g., a source) of the FET 434 is connected to a resistor 436and a gate of the FET 434 is connected to the voltage supply Vcc. Theresistor 436 is connected to a voltage source 438. The current source432 is a current mirror of the current source 392 (FIG. 4) of thecurrent regulator circuit 214′. The resistor 436 is a scaled version ofthe resistors 394 and 362 (FIG. 4). The resistor 436 is a scaled versionof the resistors 394 and 362. For example, the resistance is equal toN*R_(x). Likewise, the current source 432, though being a mirror ofcurrent source 392, is scaled so that the current provided is equal to(1/N)*I_(user).

The voltage source 438 represents an amount of headroom required toallow proper operation of the current sink 214′ (FIG. 4). The FET 434 iselectrically the same as the FET 360 (FIG. 4) and is fully “on.” Theregulation voltage 420 is provided between the current source 432 andthe FET 434.

In this electrical configuration, a lower regulation voltage is requiredthan in circuit 412′ for the same load 40 and the dynamic range of thecircuit 412′ is increased because circuit 412″ accounts for variationsof the FET 360 (e.g., due to temperature). In one particular example, ifa worse case scenario assumed a regulation voltage of 650 mV, thevoltage source 438 provided by the adaptive regulation voltage circuit412″ may be reduced to 150 mV, for example, at room temperature. It willbe recognized that the voltage provided by the voltage source 438 isrelated to a voltage headroom required by the current sink 214′ (FIG.4). As voltages within the circuit 412″ change, for example, due totemperature, the regulation voltage 438 will change in substantially thesame manner. Reduced power consumption by the current sink 412″ results.

While resistor 394 (FIG. 4) is shown to have a value, Rx, the same asthe resistor 362, in other embodiments, the resistor 394 (and thecurrent source 392) can be differently scaled.

Elements of different embodiments described herein may be combined toform other embodiments not specifically set forth above. Otherembodiments not specifically described herein are also within the scopeof the following claims.

What is claimed is:
 1. A circuit comprising: a switching regulatorconfigured to provide power to a load; a current regulator circuitcoupled to the load; and a response circuit configured to provide avoltage control signal to the switching regulator in response to voltagechanges from a signal received by the response circuit from the currentregulator circuit, wherein the voltage control signal changesnon-linearly with respect to the voltage changes from the signalreceived by the response circuit from the current regulator circuit. 2.The circuit of claim 1 wherein the switching regulator is a DC-DCconverter.
 3. The circuit of claim 1 wherein the response circuitcomprises an amplifier.
 4. The circuit of claim 3 wherein the amplifierreceives a first input from a regulation voltage circuit and a secondinput from the current regulator circuit.
 5. The circuit of claim 3wherein the amplifier is a non-linear amplifier.
 6. The circuit of claim3 wherein the amplifier is a linear amplifier.
 7. The circuit of claim6, further comprising a current detection circuit configured todetermine if a current at the current regulator circuit reaches apredetermined threshold level.
 8. The circuit of claim 7 wherein thecurrent detection circuit enables the linear amplifier to increase acurrent output of the linear amplifier if a current at the currentregulator circuit reaches the predetermined threshold level.
 9. Thecircuit of claim 7 wherein the current detection circuit providesadditional current if current at the current regulator circuit reaches apredetermined threshold level.
 10. The circuit of claim 1 wherein theload comprises one or more light emitting diodes (LEDs).
 11. A circuitcomprising: a switching regulator configured to provide power to a load;a current regulator circuit coupled to the load; and an adaptiveresponse circuit comprising: an amplifier configured to provide avoltage control signal to the switching regulator in response to avoltage signal from the current regulator circuit and comprising a firstinput and a second input coupled to the current regulator circuitconfigured to receive the voltage signal from the current regulatorcircuit; and an adaptive regulation voltage circuit configured toprovide a regulation voltage to the first input of the amplifier tomaintain operability of the current regulator circuit, wherein theadaptive regulation voltage circuit compensates for changes inelectrical characteristics of the current regulator circuit due tochanges in temperature.
 12. The circuit of claim 11 wherein theadaptation regulation circuit comprises a first current source thatmirrors a second current source in the current regulator circuit.